The present invention relates to an office chair. More particularly, it relates to a chair, having a chair body and a backrest and/or armrests, in which an adjusting mechanism for adjusting the height of the backrest and/or of the armrests in the direction of the vertical relative to the chair body is provided, which includes at least one securing element, which is solidly connected to the chair body on one end of the adjusting mechanism and which on its free end has a vertically or obliquely upward-extending end portion with a substantially vertically oriented oblong slot or guide slot, through which a threaded bolt, connected on one end rigidly to a handwheel, reaches that on the other end can be screwed into a thread in the backrest and/or into the armrest, as a result of which securing of the backrest and/or of the armrests to the end portion of the securing element is effected in clamping fashion.
Chairs of this kind, with backrests and optionally also armrests that are adjustable in height relative to the chair body, have long been known particularly in the field of office chairs. As a rule, such a chair has a very simple adjusting mechanism, by means of which, by firmly screwing the threaded bolt in a height position, selected by the user, along the oblong slot or guide slot, the backrest and/or an armrest can be firmly clamped in the desired vertical spacing from the chair body, in particular the seat, on the end portion of the applicable securing element.
This type of adjusting mechanism has proved itself over many decades, because on the one hand it is very uncomplicated and is inexpensive to produce and on the other it is simple to manipulate even without detailed explanations. However, a substantial disadvantage of such devices is that when the screwed connection is released by opening the screw fastening of the threaded bolt, the clamping connection between the backrest or the armrest and the securing element is immediately and uncontrollably released, causing the backrest and armrest to drop downward unless the user holds them firmly.
Adjusting the height can only be done ever with two hands, by holding the backrest or armrest that is to be adjusted in a desired position with one hand, and with the other hand, by turning the handwheel and thus screwing in the threaded bolt, a clamping connection is brought about, so that the part to be adjusted is fixed in the current height position. If the screwed connection is not strong enough, however, a clamping force may possibly not suffice to counteract gravity over time; then the part to be adjusted slips downward from the desired position or falls all the way down into the lowest possible position specified by the oblong slot or guide slot.